# In the Year of ’39

In the year of ’39 assembled here the volunteers,
In the days when lands were few;
Here the ship sailed out into the blue and sunny morn,
The sweetest sight ever seen.

Lately I’ve had this song running through my head, pretty much on constant repeat. It’s an old song, first released in 1975 on the album A Night at the Opera by Queen.

And the night followed day,
And the storytellers say
That the score brave souls inside
For many a lonely day sailed across the milky seas,
Ne’er looked back, never feared, never cried.

At first it seems to be telling a relatively ordinary story. Volunteers set sail in a ship for a dangerous journey. Is it 1939? Is this something to do with World War II? It’s not really clear yet.

Don’t you hear my call though you’re many years away,
Don’t you hear me calling you;
Write your letters in the sand
For the day I take your hand
In the land that our grandchildren knew.

Wait, what? The land that our grandchildren knew? Ok, there is something odd going on here. And what’s this about being many years away? The song seems to be playing around with time.

In the year of ’39 came a ship in from the blue,
The volunteers came home that day,
And they bring good news of a world so newly born,
Though their hearts so heavily weigh;

For the Earth is old and grey,
Little darling went away,
But my love this cannot be,
For so many years have gone though I’m older but a year,

Right, this is definitely not an ordinary ship sailing ordinary seas, and time is certainly being twisted. The volunteers bring news of a new world, while the Earth is old and grey? We’re talking about space travel, aren’t we? In fact, we’re talking about interstellar travel.

It’s definitely not 1939.

Many music lovers might have been confused by this song, but by now it should be obvious to readers of this blog what’s going on here. For astronauts to travel far enough to discover another world (“so newly born”), one capable of replacing the “old and grey” Earth as humanity’s home, and return back with the news “older but a year,” they must have traveled very fast indeed. Perhaps even approaching the speed of light?

At speeds this fast, the theory of special relativity tells us (and experimental research has shown) that odd things happen with time. Time appears to slow down for the traveler, at least relative to the stationary observer, so that by journey’s end the traveler will have aged far less than those who stayed home.

In the year of ’39 assembled here the volunteers

2139, perhaps? 2239? It’s not completely clear.

In the year of ’39 came a ship in from the blue,
The volunteers came home that day

Not the same ’39, but 100 years later. 2239? 2339?

For so many years have gone though I’m older but a year

As it happens, given the parameters of the song, we can calculate how fast the ship was traveling, and thus how far away they went, and perhaps even speculate what star they visited! This is because, despite being such a non-intuitive phenomenon, time dilation due to relativistic effects is well understood, and there is an equation to calculate it.

$t'=t\sqrt{1-\frac{v^2}{c^2}}$

Where:

t’ = dilated time
t = stationary time
v = velocity
c = speed of light

We want to know the ship’s velocity, so let’s parse this out (like traveling back in time to algebra class!):

$t'^2=t^2\times({1-\frac{v^2}{c^2}})$

$\frac{t'^2}{t^2}=1-\frac{v^2}{c^2}$

$\frac{t'^2}{t^2}+\frac{v^2}{c^2}=1$

$\frac{v^2}{c^2}=1-\frac{t'^2}{t^2}$

$v^2=(1-\frac{t'^2}{t^2})\times c^2$

$v=\sqrt{(1-\frac{t'^2}{t^2})}\times c$

Ok, let’s plug in some numbers! To keep things simple, we’ll express velocity as a percentage of the speed of light, and time in years, even though normally in physics equations velocities would be meters per second and time in seconds. But at this scale, those would be some big numbers, so we’re going to assume that c=1, and that v therefore is a percent of c.

$v=\sqrt{(1-\frac{1^2}{100^2})}\times 1$

$v=\sqrt{1-\frac{1}{10000}}$

$v=\sqrt{1-0.0001}$

$v=\sqrt{0.9999}$

$v=0.99995$

In order for 100 years to have passed on Earth while only 1 year passed for the astronauts, the ship had to be traveling approximately 99.995% of the speed of light. That is some extreme time dilation, and so that is some extreme speed. Quite the starship!

Time isn’t the only thing dilating here, as traveling at these speeds does some interesting things to the fabric of space as well. Distances ahead of the travelers will appear to shrink somewhat, though even at this high fraction of the speed of light, it’s a minimal effect. Add a few more 9s to the significant digits, however, and it gets very strange indeed.

Meanwhile, though, our travelers have spent a year journeying at very close to the speed of light. How far have they gone? One light-year?

Oh no. They’ve gone much farther than that. The distance traveled is at a speed relative to time for the stationary observers waiting patiently back on Earth, so our starship has traveled a hundred light-years, though it seems to the astronauts to take only one year to do so.

So, what star might they have visited to find a “world so newly born” to which humanity could relocate? First off, this was a round-trip, so with half the time spent journeying out and half spent returning, that would imply they went no more than fifty light-years away (“no more than,” I say, as if this is no big deal, but fifty light-years is a very big deal). Gliese 163 is 49 light-years away and has one potentially habitable world, but it’s not considered an absolutely prime candidate.

Let’s assume, for a moment, that our starship took a little bit of time to accelerate and then decelerate on its journey, so that instead of 50 light-years, perhaps it really only traveled about 40 light-years away.

They went to Trappist-1.

Trappist-1 is a cool red dwarf star 39.6 light-years away, and it has seven temperate and terrestrial planets, four of which are considered potentially habitable even by conservative estimates. Trappist-1 is obviously a prime candidate for finding life, or at least worlds on which humans could live, and being at about the right distance, is also a prime candidate for our volunteers on their desperate and lonely journey.

Not that this provided much consolation to our narrator, who returns to Earth to find his wife long dead, and only a memory of her in the eyes of his (presumably centenarian) daughter (or granddaughter?).

’39 was written by Brian May, lead guitarist for Queen, in 1975. May, as some of you may know, is also an accomplished astrophysicist, and while the planets of Trappist-1 had not yet been discovered in 1975, he certainly understood the effects and impacts of time dilation on travel at relativistic speeds. May studied physics and mathematics up through the time when his music career began to skyrocket to success, though due to focusing on music after that point, it took him 37 years to complete his doctoral thesis (A Survey of Radial Velocities in the Zodiacal Dust Cloud), finally earning his PhD in 2008. He was Chancellor of Liverpool John Moores University from then until 2013, and he was a science team collaborator for the NASA New Horizons mission to Pluto.

Not just a fantastic guitarist and songwriter, but a serious scientist!

Don’t you hear my call though you’re many years away,
Don’t you hear me calling you;
All your letters in the sand cannot heal me like your hand,
For my life
Pity me.

Final note: Although Freddie Mercury is far more well-known as lead vocalist, it was Brian May who sang the lyrics for the studio version of ’39 (though Mercury sang for most of their live performances).

’39 from the album A Night at the Opera by Queen, 1975
Songwriter Brian May, copyright EMI Music Publishing, Sony/ATV Music Publishing LLC

Special thanks to E=mc2 Explained for breaking down the physics of time dilation for us laypeople.

Header image credit: user:Les Chatfield / flickr.com under CC-BY 2.0

## 3 thoughts on “In the Year of ’39”

1. Linda Phelps

Aside from author, you are now a teacher.Thanks for that Matt,.

Liked by 1 person

1. Thank you, Linda! I’m always learning something myself when I put one of these posts together, and I hope my head wasn’t too far into the clouds when I put my thoughts down on the page. Mostly, though, I just hope you enjoyed my little ramble down relativity lane.

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